The invention relates to a procedure for producing an integrated system of thin-film solar cells connected in series, which have on a substrate a series of layers consisting of a first electrode layer, a photosensisive layer composed of sublayers, and a second electrode layer.
A procedure of this nature is known from, for example, the DE-OS No. 28 39 038. The arrangement described there is intended for the production of series connected systems of barrier layer photoelectric cells, in which a first electrode layer consisting of tin oxide is initially applied on a glass substrate and subsequently a photosensitive layer consisting of cadmium sulphide and of copper(I) sulphide (cuprous sulphide). For the purpose of separating individual solar cells as well as in preparation of the series connection of the cells, predetermined areas of the photosensitive layer and the first electrode layer subjacent to it are removed. In the first case, this is done by punching or miter cutting, and, in the second case, by electro-erosion, laser irradiation, masking or etching. The removed areas of the photosensitive layer are significantly broader than the section of the subjacent electrode layer which needs to be removed. The latter do not lie in the center of the layer gaps of the photosensitive layer but are displaced toward a margin. In a subsequent processing step insulating materials are applied on both sides of the gap in the photosensitive layer. One of these two insulating masses reaches into the relatively narrow layer gaps of the electrode layer. Between both insulating masses, an adhesive agent is applied to the exposed surface of the electrode layer and subsequently a second electrode layer, consisting of copper, is vapor-deposited over the entire surface of this structure. By applying ultransonic energy in the area of one of the insulating masses, which do not reach into the gaps of the first electrode layer, this insulating mass with the copper layer above it is eroded so that a structure is obtained in which, through the remaining copper layer, the first electrode layer of a solar cell is electrically connected with the upper side of the photosensitive layer of the adjacent solar cell.
Over all, this known production method is relatively expensive. The required extensive large-area separating processes have to be interrupted following the application of the second layer, namely the photosensitive layer, in order to structure the already applied layers as well as to insert into the layer gaps created in this way an adhesive agent and two insulating masses in each instance. The latter insulating masses, moreover, need to be selected from different materials, since only one of the materials is intended to respond to the later employed ultrasonic energy. Only then is the third layer, namely the second electrode layer, applied over a large area, which now, however, covers one of the insulating substances, which has actually become superfluous and therefore has to be sonically eroded together with the area of the second electrode layer lying above it. Only in this way is the second electrode layer structured. Such production methods seem, in view of the overall demand in terms of process expenditures, in need of improvement.